Memoria para optar al Título Profesional de Ingeniero Agrónomo Mención Enología y Vitivinicultura / En el presente estudio se evaluó el efecto de la criomaceración y diferentes fechas de cosecha sobre la composición fenólica, características químicas y sensoriales de los vinos de los cultivares Cabernet Sauvignon y Chardonnay. Se utilizaron uvas provenientes del Valle del Maipo cosechadas durante la vendimia 2003, las cuales fueron sometidas a criomaceración durante 10 días para su posterior vinificación. A la materia prima de cada uno de los tratamientos, se les realizó análisis básicos determinándo, entre otros, densidad, pH y acidez. Durante el período que duró la criomaceración y la fermentación alcohólica se realizaron diariamente análisis de compuestos fenólicos tales como fenoles totales, intensidad colorante, taninos totales y, en el caso de los tratamientos de la cepa Cabernet Sauvignon, antocianos totales. Al término de la vinificación y luego de darles 2 meses de reposo en botella, a los vinos resultantes se les realizaron los mismos análisis de compuestos fenólicos además de grado de polimerización de taninos y los índices de etanol y gelatina. Para la determinación de compuestos fenólicos de bajo peso molecular y antocianos se utilizó un equipo de cromatografía líquida de alta eficiencia acoplado a un detector de fotodiodos alineados (HPLC-DAD).

Thermal processing has been used as a means of modifying the sensory aspects of wine. Cabernet Sauvignon wines were heated prior to dejuicing (3C per day from 25C to 42C) or after bottling (42C for 21 days) to determine the effects on total glycosides and glycosidic fractions. Total and phenol-free glycosidic concentrations in the wine and skins were quantified by analysis of glycosyl-glucose. Pre-dejuicing thermal vinification resulted in higher total glycosides (12%), phenol-free glycosides (18%), total hydroxycinnamates (16%), large polymeric pigments (LPP) (208%) small polymeric pigments (SPP) (41%), and lower monomeric pigments (42%) in wines. Skins had lower total glycosides (-16%), and no significant difference in phenol-free glycosides. Post-bottling heat treatment resulted in lower total (-15%) and phenol-free (-16%) glycosides, increased hue (25%), a 62% increase in LPP and a 29% decrease in monmeric pigments. A second study investigated the potential of enological spoilage microorganisms to affect wine aroma, flavor, and color. The activities of b-glucosidase were determined in model systems for fourteen strains of Brettanomyces bruxellensis yeast and nine strains of lactic acid bacteria (Oenococcus oeni). All Brettanomyces strains and seven Oenococcus strains exhibited enzymatic activity. B. bruxellensis b-glucosidase activity was primarily intracellular; O. oeni showed some extracellular activity. Yeasts and bacteria showing activity greater than 1000 nmole mL-1 g -1 for Brettanomyces, or 100 nmole mL-1 g -1 for Oenococcus, were evaluated for their effect on Viognier grape glycosides. Neither was active on native grape glycosides. / Master of Science

Quantification of grape glycosides has been suggested as an objective index of grape quality. Two studies were undertaken to observe the influence of vineyard management on grape glycosides. In the first study, three crop levels from mature Cabernet Sauvignon (<i>Vitis vinifera</i> L.) vines grown in eastern Virginia were evaluated for their influence on grape glycosides, expressed as red-free glycosyl glucose (GG). Crop levels averaged 3.2, 5.1, and 6.4 kg/vine resulting in leaf area to fruit weight ratios (cm²/g) of 34.4, 27.0 and 19.2, respectively. Red-free GG was greatest in juice from fruit of the low treatment at four of seven sampling dates, including harvest. Phenolic glycosides were found to comprise as much as half of the total GG value. In a second study, shoot thinning, mechanical and hand fruit zone leaf removal of mature Cabernet Sauvignon grapevines were evaluated for their influence on red-free GG. Two shoot densities were examined, each with no leaf removal (No LR), mechanical leaf removal (M LR) or mechanical plus hand leaf removal (M+H LR) imposed five weeks post-bloom. Red-free GG was increased by leaf removal of shoot thinned vines and was greatest with mechanical plus hand leaf removal. / Master of Science

Les flavanols et leurs oligomères, les procyanidines, sont des composés phénoliques biosynthétisés dans les baies de raisin, dont ils sont extraits pendant la vinification. Une meilleure compréhension de leur évolution pendant la maturation du raisin, la vinification et le vieillissement du vin est importante du fait de leur responsabilité dans beaucoup des propriétés organoleptiques du vin (couleur, amertume et astringence). Plusieurs procyanidines ont été obtenues par une méthode de synthèse permettant de contrôler aussi bien la régio- et la stéréosélectivité de la liaison interflavane que le degré d’oligomérisation. Cette méthode a pu être élargie à la synthèse de procyanidines galloylées. L’étape de couplage, qui restait l’étape limitante de cette synthèse, a pu être améliorée par l’utilisation de la catalyse à l’or. Ces composés ont ensuite été utilisés comme standards afin de les identifier et les quantifier dans du raisin et des vins par chromatographie liquide haute performance. L’étude des intéractions supramoléculaires des composés galloylés a été évaluée par RMN DOSY. En parallèle de ces études, un nouveau composé indolique, possédant un motif glucose dans sa structure, a été identifié et caractérisé pour la première fois dans les vins rouges. / Flavanols and their oligomers, procyanidins, are phenolics compounds biosynthetized in grapes, from which they are extrated during winemaking As they contribute so much to the organoleptics properties of the wine (color, bitterness and astringency), a better comprehension of their evolution during grapes maturation, winemaking and ageing of the wine is particulary important. Several procyanidines were obtained by a synthesis method which allows to control as well the interflavan regio- and stereoselectivity as the degree of oligomerization. This method was extended to the synthesis of galloylated procyanidins. The stage of coupling, which was a limiting stage of this synthesis, could be improved by the use of gold III catalysis. These compounds were then used as standards in order to identify and quantify them in grapes and wines by high performance liquid chromatography. The supramolecular properties of galloylated procyanidins were investigated by NMR DOSY. In parallel to these studies, a new indolic compound bearing a glucose moiety, has been identified and characterized for the first time in red wine.

La réduction des effets secondaires des produits phytosanitaires sur l’environnement est un enjeux majeur du Grenelle de l’environnement. L’utilisation prolongée du cuivre comme fongicide a entrainé son accumulation dans les sols viticoles. Le cuivre étant phytotoxique,son accumulation dans la plante pourrait modifier la morphologie, la biochimie ou la physiologie des organes végétaux et perturber les interactions vigne-bio-agresseur. Nousavons donc évalué les effets de la contamination cuprique des sols viticoles sur la sensibilitéde la vigne à un cortège de bio-agresseurs par une approche plus intégrée de la culture et deson patho-système.Pour cela, nous avons mesuré les teneurs en cuivre total et disponible des parcelles viticoles.Nous avons exposé au cuivre trois cépages puis nous avons mesuré la distribution du cuivre et ses effets dans la plante. Enfin nous avons évalué l’impact induit pour trois bio-agresseurs de la vigne. Nos résultats montrent que la teneur en cuivre disponible du sol dépend surtout de la teneur total en cuivre (qui résulte de l’historique parcellaire) mais aussi des teneurs en carbone total et en particules fines du sol. L’absorption du cuivre et son transfert vers les parties aériennes varient selon les cépages. Lorsque la contamination cuprique augmente, les interactions vigne-bio-agresseurs sont modifiées : si les effets semblent négatifs pourScaphoideus titanus et Plasmopara viticola, la contamination cuprique semble favorable au développement de Neofusicoccum Parvum. Ces résultats soulignent la nécessité d’avoir une vision la plus intégrée possible du système, et d’intensifier les interactions de recherches entre l’agronomie et l’écologie évolutive. / Following the ‘Grenelle of the environment’ conference, one of the current critical issues in agriculture is reducing the side effects of pesticides on the environment. Prolonged use of copper as a fungicide has led to copper accumulation in vineyard soils. Copper can induce aphytotoxicity. Its accumulation in plants may modify the morphology, biochemistry orphysiology of plant organs and may disturb the plant-pest interactions. The effects of coppercontamination of vineyard soils on the vine sensitivity to the pests received until now a verylimited attention. The present work investigates such effects.To carry out this work, we measured the levels of total and available copper in vineyard soils.We contaminated three grapevine cultivars with copper and measured the copper distributionand its effects on plant. Then, we evaluated the impact induced on three pests of the vine. Ourresults show that the available copper content in the soil is related to the total copper content(which results from the history of the plot), but also to total carbon and fine soil particlescontents. The copper absorption and the copper transferred to the aerial parts of the vine varyaccording to the cultivar. When copper contamination increases, the vine-pests interactionsare modified: a negative effects appears for Scaphoideus titanus and Plasmopara viticola,while important copper contaminations appears to promote the development ofNeofusicoccum parvum.These results underscore the need for a more integrated system approach, and to intensifyinteractions between agronomy and evolutionary ecology research.

La mise au point de techniques de fractionnement des moûts de Sauvignon blanc par chromatographie de partage centrifuge et par chromatographie Flash, a permis de mettre en évidence la présence de deux « nouvelles » formes précurseurs du 3SH (le S-3-(hexan-1-al)-glutathion et l'acide S-3-glutathionyl-hydroxyhexanesulfonique). L’ensemble de ces résultats a permis de confirmer la contribution majeure des S-conjugués au potentiel en 3SH des moûts. Le S-3-(hexan-1-ol)-L-cystéine, le S-3-(hexan-1-ol)-glutathion ainsi que les deux nouvelles formes identifiées, permettent d’expliquer près de 65% du 3SH libéré dans les vins. Par ailleurs, nous avons montré que l’ensemble des formes précurseurs appartenait à la même voie d’assimilation de la levure et que le S-3-(hexan-1-ol)-L-cystéine est un intermédiaire indispensable à la biotransformation des S-conjugués au glutathion, précurseurs du 3-sulfanylhexanol. De plus, le pourcentage de biotransformation des différents S-conjugués en 3SH semble directement lié à leur position dans le flux métabolique. / The development of fractionation techniques in Sauvignon Blanc musts such as centrifugal partition chromatography and flash chromatography, permitted to identify two precursor forms of 3-sulfanylhexanol : the S-3-(hexan-1-al)-glutathione, and the S-3-glutathionyl-hydroxy hexanesulfonic acid. These results confirmed the major contribution of S-conjugates in the potential liberation of 3-sulfanylhexanol in musts. The two newly identified forms along with S-3-(hexan-1-ol)-L-cysteine and S-3-(hexan-1-ol)-glutathione, explain up to 65% of the total release of 3-sulfanylhexanol. Futhermore, we showed that all precursor forms belonged to the same assimilation pathway of yeast and the S-3-(hexan-1-ol)-L-cysteine is an essential intermediate in the metabolism of S-glutathione conjugates, which is a precursor of 3-sulfanylhexanol . Finally, the biotransformation percentage of different S-conjugates of 3-sulfanylhexanol seems directly related to their position in the metabolic flow.

Thesis (MSc (Wine Biotechnology))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: The varietal character of Sauvignon blanc wine is mostly defined by the balance between tropical and green vegetative flavour nuances. Grape derived methoxypyrazines are the main aroma contributors towards green vegetative flavours. Methoxypyrazines are heat and light sensitive. Due to warm climatic conditions in South Africa, methoxypyrazine levels decrease during grape ripening. The addition of food flavourings to Sauvignon blanc wine, a practice known as spiking, has occurred in the past to improve the green character of the wines. Adding flavourings to wine and selling the wine as natural certified wine is illegal in South Africa. Currently, adulterated Sauvignon blanc wines are identified using gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–mass spectrometry (LC-MS) methods to quantify methoxypyrazines and compare levels to an established database. Although of high sensitivity, GC-MS and LCMS methods are costly and time consuming, therefore not optimal for routine screening of wines. Hence the need for the development of a fast and cost effective method for routine screening of large amounts of wines to identify adulteration. Small scale vinification practices were used to prepare experimental Sauvignon blanc wine. Flavourings were added to Sauvignon blanc grape juice before fermentation, during the preparation of experimental spiked wines. Control wines, containing no flavouring, were also prepared. Commercial wines were spiked after fermentation and bottling. Each wine was only spiked with a single flavouring. The flavourings added were the juice of homogenised fresh green peppers and commercially available flavourings for wine. The following commercial flavourings were used: green pepper, asparagus, grassy and tropical. The above mentioned wines were analyzed using Fourier transform infrared (FT-IR) spectroscopy, GC-MS, LC-MS and descriptive sensory analysis. The FT-IR techniques used were Fourier transform mid infrared (FT-MIR) transmission, FT-MIR attenuated reflection and Fourier transform near infrared (FT-NIR) reflection spectroscopy. The data was interpreted using the following multivariate statistical techniques: principal component analysis (PCA), partial least squares discrimination (PLS-D) and conformity testing. Multivariate models constructed from FT-MIR and FT-NIR data were able to discriminate between spiked and control wines. Sensory analysis results clearly showed differences between non-spiked wines and spiked wines with 3-isobutyl-2-methoxypyrazine concentrations 10 times higher than naturally occurring in wine. Differences between control and spiked wines with concentrations of 3-isobutyl-2-methoxypyrazine similar to concentrations naturally occurring in wines could not be detected to prove adulteration conducting sensory analysis. However, differences between control and spiked wines with levels of 3-isobutyl-2-methoxypyrazine similar to levels naturally occurring in wines could be detected using FT-IR data in conjunction with multivariate statistics. This study showed that, FT-IR spectroscopy in conjunction with multivariate statistical methods can be a possibility for the screening and identification of wines suspected of adulteration in terms of added flavourings. Descriptive sensory analysis also proved to be a potentially useful tool. However screening and training of potential panel members are time consuming. / AFRIKAANSE OPSOMMING: Die variëteitskarakter van Sauvignon blanc wyn word grotendeels gedefinieer deur die balans tussen tropiese en groen vegetatiewe aromas. Metoksipirasiene is die hoof aroma verbindings wat verantwoordelik is vir groen vegetatiewe aromas. Metoksipirasien is hitte- en ligsensitief. Warm klimaatsomstandighede in Suid-Afrika het tot gevolg dat metoksipirasien konsentrasies daal tydens druif rypwording. Sauvignon blanc wyne is in die verlede vervals deur middel van die byvoeging van vars groen soetrissies om die groen vegetatiewe karaktereienskappe van die wyne te bevorder. Die byvoeging van geurmiddels of plantekstrakte by wyn en verkoop van daardie wyn as gesertifiseerde natuurlike wyn is onwettig in Suid-Afrika. Tans word vervalsde wyne met behulp van gaschromatografie-massaspektrometrie (GC-MS) en vloeistofchromatografie-massaspektrometrie (LC-MS) opgespoor. Kwantifisering van metoksiepirasien konsentrasies in wyne en druiwesappe word vergelyk met konsentrasies in ‘n bestaande databasis. Alhoewel GC-MS en LC-MS hoë sensitiwiteitsmetodes is, is dit duur en tydrowende metodes, dus nie optimaal vir roetine sifting nie. Dus word ‘n koste- en tydseffektiewe roetine metode benodig om vervalsing van wyne op te spoor. Eksperimentele wyne is op klein skaal berei. Geurmiddels is voor fermentasie by die druiwesap gevoeg. Kontrole wyne waarby geen geurmiddels gevoeg is nie, is ook berei. Kommersiële wyne is gegeur na fermentasie en bottelering. Elke wyn is met ‘n enkele geurmiddel gegeur. Gehomogeniseerde vars groen soetrissie asook kommersieel beskikbare geursels vir wyn is gebruik. Die volgende kommersiële geursels is gebruik: groen soetrissie, aspersie, gras en tropiese geursel. Die volgende analitiese tegnieke is gebruik vir analisering van bogenoemde wyne: Fourier transformasie infrarooi (FT-IR) spektroskopie, GC-MS, LC-MS en beskrywende sensoriese analise. Die spesifieke FT-IR tegnieke wat gebruik is, is: Fourier transformasie mid-infrarooi (FT-MIR) transmissie, FT-MIR verswakte weerskaatsing en Fourier transformasie naby-infrarooi (FT-NIR) reflektansie. Die volgende multiveranderlike statistiese tegnieke is gebruik ter interpretasie van data: hoof komponent analise (PCA), parsiële kleinste kwadraat diskriminant analise (PLS-D) en gelykvormigheidstoetsing. Multiveranderlike modelle, bereken met behulp van FT-MIR en FT-NIR data, kon diskrimineer tussen gegeurde en kontrole wyne. Resultate wat verkry is tydens sensoriese analises het duidelike verskille uitgewys tussen gegeurde en kontrole wyne met betrekking tot 3-isobutiel-2- metoksipirasien konsetrasies waar 3-isobutiel-2-metoksipirasien konsentrasies 10 keer hoër was as wat natuurlik voorkom in wyn. Geen beduidende verskille kon waargeneem word in gevalle waar wyne vervals is met laer konsentrasies van geurmiddels deur sensoriese data te ontleed nie. Nietemin, statisitiese verskille tussen kontrole en vervalsde wyne kon waargeneem word vir lae-konsentrasie-geurmiddel vervalsde wyne deur FT-IR data met behulp van multiveranderlike statisitiese metodes te ontleed. Hierdie studie het gewys dat FT-IR in kombinasie met multiveranderlike statistiese tegnieke spesifiek hoof komponent analise (PCA) en parsiële kleinste kwadraat diskriminant analise (PLS-D) asook gelykvormigheidstoetsing bruikbare tegnieke is om te onderskei tussen kontrole (egte natuurlike) en vervalsde wyne ten opsigte van die byvoeging van geurmiddels. Beskrywende sensoriese analise kan ook nuttig gebruik word, alhoewel keuring en opleiding van paneellede tydrowend is.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Grape must is a complex medium, and during wine production numerous biochemical pathways and metabolic reactions are taking place simultaneously to produce a specific taste and aroma. Microorganisms, specifically yeast, play a key role in the formation of metabolites formed during alcoholic fermentation. Sauvignon blanc, a well studied grape cultivar, is known to have a versatile range of aroma profiles ranging from “green” to “tropical”. It has been broadly stated that a “green” Sauvignon blanc can be created in the vineyard and a “tropical” Sauvignon blanc can be created by selecting a specific yeast strain, and that the balance between “green” and “tropical” characters is essential for the final aroma profile. Except for grape-derived varietal aromatic compounds such as methoxypyrazines (green), volatile thiols (tropical) and monoterpenes (floral), yeast derived volatile compounds including esters, higher alcohols, fatty acids and carbonyl compounds will also contribute to the final wine aroma. The main aim of this study was to assess how viticultural treatment-derived differences in grape must, can impact on aroma production when this grape must is fermented with different commercial wine yeast strains. The viticulture treatment focused on light intensity modulated through canopy treatment. Volatile aroma differences were compared for canopy and yeast treatments, specifically focusing on the fermentation derived bouquet (esters, higher alcohols, volatile fatty acids, carbonyl compounds and monoterpenes). Results showed significant differences between initial must compositions, including titratable acidity, malic acid and yeast assimilable nitrogen. The volatile aroma compounds were also significantly impacted although no noticeable effect on the overall fermentation kinetics was observed. Depending on the yeast strain differences in volatile compounds varied. A clear vintage effect is noticeable between volatile compounds affected by the treatments. Data generated in 2012 shows clear differences between ethyl- and acetate esters and could clearly be grouped according to yeast strain through multivariate analysis. Sensory evaluation results could clearly be distinguished according to canopy treatment and to a lesser degree according to yeast strain used. This indicates that although yeast has a more prominent impact on the fermentative bouquet that develops during alcoholic fermentation the overriding aroma is primarily derived from grape-derived metabolites which can be manipulated by canopy treatments. None the less the difference in fermentation bouquet does add to the complexity of the wine especially in the case of fermentation derived “tropical” aromas including guava and passion fruit. In some cases where shaded grapes had higher ester concentrations, the resultant wine also had higher aroma quality. This study has contributed to a better understanding of the complex relationships between canopy manipulation and yeast selection on aroma formation. The analysis of volatile aroma alone however is not enough to understand the final perception of wine taste and further indepth studies of the viticultural and oenological factors is needed. In particular, this project has focused on a single vineyard over only two vintages. The general validity of the conclusions derived from this study therefore will require additional data sets. / AFRIKAANSE OPSOMMING: Druiwemos is ‘n komplekse medium en tydens wynbereiding is daar verskeie biochemiese weë en metaboliese reaksies wat gelyktydig plaasvind om ‘n spesifieke smaak en aroma te produseer. Mikro-organismes, veral gis, speel ‘n sleutelrol in die vorming van metaboliete tydens alkoholiese gisting. Sauvignon blanc, ‘n goed bestudeerde druifkultivar, besit ‘n veelsydige reeks aromaprofiele wat wissel van “groen” tot “tropies”. Oor die algemeen word dit voorgehou dat ‘n “groen” Sauvignon blanc in die wingerd geskep word, terwyl ‘n “tropiese” Sauvignon blanc geskep kan word deur ‘n spesifieke gisras te selekteer, en die balans tussen “groen” en “tropiese” karakters is noodsaaklik vir die finale aromaprofiel. Behalwe vir druifafgeleide kultivarafhanklike aromatiese verbindings soos metoksipirasiene (groen), vlugtige tiole (tropies) en monoterpene (blomagtig), sal gisafgeleide vlugtige komponente, waaronder esters, hoër alkohole, vetsure en karbonielverbindings, ook tot die finale wynaroma bydra. Die hoofdoelwit van hierdie studie was om te bepaal hoe verskille in druiwemos wat afkomstig is van wynkundige behandeling ‘n impak op aromaproduksie kan hê wanneer hierdie druiwemos met verskillende kommersiële wyngisrasse gegis word. Die wynkundige behandeling het gefokus op ligintensiteit wat deur lowerbehandeling gereguleer is. Vlugtige aromaverskille is op grond van lower- en gisbehandelings vergelyk, met ‘n spesifieke fokus op die gistingsafgeleide boeket (esters, hoër alkohole, vlugtige vetsure, karbonielverbindings en monoterpene). Die resultate het beduidende verskille getoon tussen aanvanklike mossamestellings, waaronder titreerbare suurheid, appelsuur en gis-assimileerbare stikstof. Daar was ook ‘n noemenswaardige impak op die vlugtige aromaverbindings, hoewel geen merkbare effek op die algehele gistingskinetika waargeneem kon word nie. Die verskille in vlugtige verbindings het gewissel op grond van die gisras. ‘n Duidelike oesjaareffek was merkbaar tussen vlugtige verbindings wat deur die behandelings geaffekteer is. Data wat in 2012 gegenereer is, toon duidelike verskille tussen etiel- en asetaatesters en kon duidelik m.b.v. meervariantanalise volgens gisras gegroepeer word. Die resultate van die sensoriese evaluering kon duidelik volgens lowerbehandeling onderskei word, en tot ‘n mindere mate volgens die gisras wat gebruik is. Dít dui daarop dat hoewel gis ‘n meer prominente impak het op die gistingsboeket wat tydens alkoholiese gisting ontwikkel, is die oorheersende aroma hoofsaaklik afgelei van druifafgeleide metaboliete wat deur lowerbehandelings gemanipuleer kan word. Nietemin dra die verskil in gistingsboeket by tot die kompleksiteit van die wyn, veral in die geval van gistingsafgeleide “tropiese” aromas, insluitend koejawel en grenadella. In sommige gevalle waar beskadude druiwe hoër esterkonsentrasies gehad het, het die gevolglike wyn ook ‘n hoër aromakwaliteit gehad. Hierdie studie dra by tot ‘n beter begrip van die effek van die komplekse verhoudings tussen lowermanipulasie en gisseleksie op aromavorming. ‘n Analise van vlugtige aroma alleen is egter nie voldoende om die finale persepsie van wynsmaak te begryp nie en bykomende diepgaande studies van die wingerdkundige en wynkundige faktore word benodig. Hierdie projek het in die besonder gefokus op ‘n enkele wingerd oor slegs twee oesjare. Die algemene geldigheid van die afleidings wat van hierdie studie gemaak word, sal dus bykomende datastelle vereis. / The National Research Foundation and Postgraduate Merit Bursary for financial support

The effects of crop load and berry exposure on the composition of Marlborough Sauvignon blanc grapes and wine from the Brancott vineyard, Blenheim, were explored. Commercially grown, 2-cane and 4-cane Sauvignon blanc vines were used with a row orientation of north-south. Two exposure treatments were imposed in the following manner: complete leaf removal was undertaken in the fruit zone and 50% shade cloth was erected to give a uniform shading treatment to half the trial vines. Weekly thirty-berry and whole bunch samples were taken from each of the 32 plots with the exception of the veraison period when two samples per week were taken. Vine vigour was assessed using pruning and leaf area per vine data. Harvest occurred on different dates for 2-cane and 4-cane pruned vines so that fruit attained from both treatments had similar °Brix. Fruit was processed at the Lincoln University winery. Must analysis and wine analysis were undertaken. As expected, 4-cane vines had almost double the yield of 2-cane vines. Higher crop load significantly reduced leaf area per shoot and shoot thickness. Lower leaf area to fruit ratio for 4-cane berries resulted in delayed onset of veraison and slowed the rate of sugar accumulation. Crop load, which limited leaf area to fruit ratio, appeared to be the dominant factor in determining timing of grape physiological ripeness as expressed by °Brix over other factors such as fruit exposure. Malic acid, tartaric acid, IPMP (iso-propylmethoxypyrazine) and IBMP (iso-butyl-methoxypyrazine) were lower at equivalent °Brix in 4-cane compared with 2-cane berries. Significantly higher concentrations of quercetin were found in exposed compared to shaded berries. Must analysis showed a significant influence of crop load on berry titratable acidity and pH, reflecting berry ripening results. Exposure significantly increased the concentrations of nitrogenous compounds in 4-cane must yet showed no influence on 2-cane must. After wine processing lower malic acid concentrations in wines made from 100% exposed fruit became evident in lower wine titratable acidity but showed no influence on wine pH. Bentonite addition to wines had a small but statistically significant influence on wine by reducing pH, titratable acidity and alcohol. Bound sulphur concentrations were significantly higher in 4-cane versus 2-cane wines. At harvest, methoxypyrazine levels in grapes and wines were very low; IBMP concentrations where significantly lower than those normally found in Sauvignon blanc wines from Marlborough. This was attributed to the absence of basal leaves from the shoots of ripening berries. The results suggest that leaf area to fruit ratio is a powerful determinant of grape and wine quality.

ABSTRACT A core tool of sensory science is the use of trained descriptive panels. This research describes an investigation into the role of motivation in the performance of trained panels and the use of a trained panel to develop a better understanding of the perception of Sauvignon blanc wines. Substantial investment in time and money is directed towards ensuring trained panels perform optimally. Having selected a panel, the panel leader needs to ensure that panellists provide accurate, reliable data. Panellist motivation is also an important factor to consider. While performance psychology, education and sport science fields have researched motivation extensively, knowledge about panellist motivation within sensory science is limited. However, findings from existing research in these other areas - which suggest an important role for autonomy, competence and relatedness - can be applied to sensory panels in order to increase intrinsic motivation. The initial part of the research investigated the fundamental factors that affect and influence panellists’ motivation and participation. A survey (n=74) revealed that extra income and a general interest in food were the key drivers in inspiring people to become panellists, whilst enjoyment in being a panellist, interest in food, and extra income were key drivers for people to remain panellists. In a second survey, the intrinsic motivation of seven trained panels from four countries (n=108) was assessed. External panels were found to be more intrinsically motivated than internal panels. Experienced panellists had an increased perception of competence, which is a key factor for people to be intrinsically motivated. Understanding motivational frameworks currently used in other research fields and integrating them into existing panel training protocols may enhance and sustain panellists’ intrinsic motivation. A trained panel (n=14) was then used in the second part of the thesis to identify key flavours in Sauvignon blanc wines from Australia, France, New Zealand, Spain, South Africa and USA. Sixteen characteristics were identified and measured, including sweet sweaty passionfruit, capsicum, passionfruit skin/stalk, boxwood/cat’s urine, grassy, mineral/flinty, citrus, bourbon, apple lolly/candy, tropical, mint, fresh asparagus, canned asparagus, stonefruit, apple and snowpea. Principal component analysis was used to describe differences between regions and countries. Sauvignon blanc wines from Marlborough, New Zealand (NZ), were described by tropical and sweet sweaty passionfruit characteristics, while French and South African Sauvignon blanc wines were described as having flinty/mineral and bourbon-like flavors. Chemical analyses of these wines also showed that Marlborough, NZ wines had more methoxypyrazine and thiol compounds. A consumer study (n=109) showed that New Zealanders significantly prefer New Zealand style Sauvignon blanc. The final part of this research focused on using trained panellists to explore the interactions between volatile and non-volatile wine compounds and their effects on the aroma profile of New Zealand Sauvignon blanc wine. Four volatile aroma compounds that are important in New Zealand Sauvignon blanc wine were studied (isobutyl methoxypyrazine [MIBP], 3-mercaptohexanol [3MH], 3-mercaptohexanol acetate [3MHA], and ethyl decanoate). Each of these four aroma compounds were assessed in combination with three non-volatile polyphenolic compounds commonly found in Sauvignon blanc wine: catechin, caffeic acid and quercetin. Results showed each polyphenol had a unique effect when blended with a specific aroma compound, either suppressing, accentuating, or showing little effect on the perception of the aroma compounds. The perception of MIBP, 3MH, and ethyl decanoate were largely suppressed by the added polyphenols, with a few exceptions. The perception of 3MH was accentuated with the addition of caffeic acid, and the perception of 3MHA was accentuated with the addition of catechin. The interactive effects of aroma compounds with polyphenols likely reflect non-covalent associations in the wine solution that reduce the volatility of the aroma compounds. With an understanding of the interactive effects of volatile and non-volatile compounds in wine, winemakers might optimize the impact of selected volatile compounds by managing polyphenol levels, supporting their efforts to attain desirable wine aroma profiles.